Yep last time I looked at it, IrDA wasn"t usable, which at the time with a laptop and phone which had it was annoying. The two are not interchangeable.
Will dig up those links if I can, but if I recall correctly, the infrared remote control signals were low rate bits, with a very high modulation frequency (twice the frequency the sound card could produce, but by using two LEDs with one reversed you could produce it on the -ve side of the soundwave).
Ok, here"s some details I"ve dug up off my HD from 2 years ago, I recall the signal I used were similar to the ones on this site (although the protocol may have differed – certainly start burst applied):
Based on this blog [http://jumpjack.wordpress.com/2008/05/
], it was possible to record and play back the signals.
By using very basic circuits I was able to directly record the IR signal through the soundcard via a IR LED, directly from the remote. The waveform is the kind of signal you get to start with.
In that form, it then needed some extra work to be usable to transmit the signal out again in the correct form…
To this end, I ended up creating a script within Audacity to do this, see the following section of the Audacity wiki (http://wiki.audacityteam.org/i.....t_Commands
You end up with something similar to:
I did also experiment with attempting to capture signals via the serial port and sending out again, but it seemed like the signals weren't very reliable.
As it happened, the soundcard method was enough to remote control my freeview box, by using a video capture card to see it and logmein to view the connected PC. Also (since the box was prone to freezing-up when transferring files from it) I could use an IR signal to reset the power too (using a IR power switch).